23 o DISCOVERY REPORTS 



genital sacs, commenced about one-third of the length of the body from the anterior 



end. 



Form and colour of preserved specimens. The colour is bleached in spirit to a greyish 

 white. No eyes are visible. The proboscis pore is terminal and the anterior end of the 

 mouth is at the level of the pos- 

 terior ends of the cephalic slits 

 (Fig. 6A). 



Internal structure. Frontal 

 organs were not seen although 

 the tip of the head was sectioned. 

 The muscle layers are arranged 

 typically (Fig. 6 B). 



There is a single vascular 

 lacuna dorsal to the rhyn- 

 chodaeum in the head. This 

 divides and the two lacunae thus 

 formed split up after the region of 



. . Fig. 6. Lmeus ruber, O. F. Muller. A, head of spirit specimen, 



the ganglia into numerous vessels ventro . latera i . B> transverse section of body at the passing of the 

 round the gut. The dorsal vessel excretory tubules to the exterior, 

 protrudes into the rhynchocoel. 



The excretory tubules bulge into the large blood vessels on each side of the rhyn- 

 chocoel. They occur a considerable distance behind the brain. Only one duct was found 

 leading to the exterior on each side and it opened high up on the dorsal surface (Fig. 

 6B). From the persistence of the tubule in the last sections cut in series of this worm 

 it is probable that further ducts were present. The number given by Punnett (i 901) is 

 from six to twelve on each side. 



The cephalic slits continue nearly to the tip of the snout and they disappear pos- 

 teriorly as soon as the canal has entered the head. The fibrous tissue of the dorsal 

 ganglion divides posteriorly into an upper branch which quickly disappears, and a lower 

 which becomes invested with the cerebral organ and forms the posterior lobe of the 

 brain. This lies almost free in a blood sinus at its hinder end. When the ventral ganglia 

 merge into the lateral nerves they shift laterally from their position directly beneath the 



dorsal ganglia. 



The genital sacs (in the female) open high up laterally. 



The green form of L. ruber was described by Stimpson (1856 and 1857-8) from speci- 

 mens collected in Simon's Bay under the name Cerebratulus oleaginus (Meckelia olivacea 

 in the earlier paper). The identification with Lineus ruber was suggested by Burger 

 (1895). L. ruber has been recorded from Madeira by Langerhans (1880). 



